bug: planet rotation on hover and click

There has been a weird bug from the beginning where planets would sometimes not start rotating on hover, simply not recognizing the input. Same with clicking. This is probably due to them being a Area2D node, and not a control node. That can likely easily be changed by wrapping the Area2D in a control node, and then applying positioning and input events to those.

Other items that are control nodes haven't had any problems with hovering so far, mainly buttons and such.